The present invention concerns nonfriction power systems, and more particularly concerns a nonfriction positive drive power system useful for extending and retracting telescopic seating and the like.
Known power systems for extending and retracting telescopic seating, such as for bleacher systems, are of two major types--friction drive systems and nonfriction drive systems. Friction drive systems include a drive wheel that frictionally engages a floor surface to move the telescopic seating. However, friction drive systems are not reliable where the floor is likely to be dirty or where liter or debris may fall onto the floor since the drive wheel will periodically lose frictional contact with the floor and spin. Nonfriction drive systems do not frictionally engage the floor, but instead include an extendable chain that extends from a power drive mechanism positioned at the rear of the telescopic seating structure. However, nonfriction drive systems tend to be relatively large, bulky and expensive. Further, the extendable chains, if not properly adjusted, can cause the telescopic seating to extend non-linearly. This condition can cause the extendable chain and/or the telescopic seating to skew, resulting in alignment difficulties. Under extreme conditions non-linear extension may cause the chain to deform, particularly at the outermost end of the chain where the chains are the weakest and experience the greatest stress. Known extendable chains and the mechanisms for driving them also tend to be quite complex and sensitive to wear, such that they require constant maintenance and adjustment to keep them in proper working condition. "Beefing up" the extendable chains and increasing the power of the drive system is generally unsatisfactory since it adds cost and bulk, and does not solve the underlying problems relating to poor distribution of stress.
Thus, a power system for extending and retracting a structure solving the aforementioned problems is desired.